Jewish religious holiday, observed on the 10th day of the lunar month of Tishri (in late September or early October). It concludes the 10 days of repentance that begin with Rosh Hashanah. Its purpose is to purify the individual and community by forgiving the sins of others and by repenting one's own sins against God. Before the destruction of the Temple of Jerusalem, the high priest performed a sacrificial ceremony that concluded with the death of a scapegoat. Today it is marked by fasting and abstention from sex. Its eve, when the Kol Nidre is recited, and the entire day of Yom Kippur, are spent in prayer and meditation.